Proposal (610) to South
American Classification Committee
Split Sirystes into two (A) or four (B)
species
Background
The cross-Andean split of Western Sirystes S. albogriseus from Eastern Sirystes S. sibilator is widely recognised and supported by long-known and
striking differences in vocalizations.
Donegan’s (2013) study of vocal variation in the genus supported this
split but also a further three-way split of eastern populations.
Part A: Split Western Sirystes S.
albogriseus from Eastern Sirystes S.
sibilator
Ridgely & Greenfield (2001), followed by
Jahn et al. (2002), Hilty (2003),
Gill & Wright (2006), Ridgely & Tudor (2009), McMullan & Navarrete
(2013) and others treat S. albogriseus ("Western
Sirystes") as a species separate from a broadly defined S. sibilator including all remaining taxa ("Eastern
Sirystes"), based mainly on differences in vocalisations discussed in
Ridgely & Tudor (1994).
Part A would change AOU-SACC treatment to
reflect widespread existing treatments in the ornithological literature and can
be considered independently of the merits of the recent publication cited
below.
Western Sirystes gives only short chips whilst
Eastern Sirystes vocalisations involve longer notes and far more complex.
Western Sirystes: http://www.xeno-canto.org/species/Sirystes-albogriseus?view=3
Eastern Sirystes: http://www.xeno-canto.org/species/Sirystes-sibilator?view=3
I know not of two more vocally different but
lumped taxa on the SACC list. This
proposal is long overdue for consideration and its acceptance should be
strongly recommended.
Part B: Split
"Eastern Sirystes" into three species
In Donegan (2013), voice of Sirystes
throughout its range was studied in detail, as well as some specimens and other
sources of records. The abstract
includes the following:
"Vocal
differentiation in the genus was studied using quantitative methods and the
determination of primary, secondary and other kinds of vocalizations for
different populations. The widely
recognized split of Western Sirystes S.
albogriseus of the Chocó (Panama, Colombia and Ecuador) from the more
widespread Eastern Sirystes S. sibilator is
strongly supported by differences in vocal repertoire and quantitative vocal
differentiation. Eastern Sirystes is
itself a superspecies comprised of three allopatric species which are vocally
differentiated (quantitatively and in repertoire) to such an extent that
species rank would be afforded under a modern biological species concept for:
(i) White-rumped Sirystes S. albocinereus
of Western Amazonia (in Venezuela, Colombia, Ecuador, Peru, Bolivia and western
Amazonas and Acre states, Brazil); (ii) Todd's Sirystes S. subcanescens of North Amazonia (in northern Amazonas, northern
Pará and Amapá states in Brazil, French Guiana and Guyana); and (iii) Sibilant
Sirystes S. sibilator (including
subspecies atimastus) of the Atlantic
and Cerrado regions (in southern Pará state South through most of the rest of
Brazil to northern Argentina and eastern Paraguay). Considerable variation in the kind of primary
and secondary vocalizations are evident between these four proposed species,
with primary vocalizations of particular taxa appearing as rare or secondary
vocalizations or not being given at all by others. The four proposed species also show
considerable morphological differences in the context of Tyrannidae."
Vocal differentiation between the Eastern races is further detailed in
the paper as follows. See the
discussion, appendices and large number of sonograms for more information.
· The most geographically distant pair: Atlantic-Cerrado versus Western
Amazonian populations, differ: (i) in the kind of primary vocalization, which
in the Atlantic-Cerrado are chattering songs and in Western Amazonia are
whistles (App. 4); (ii) diagnosably in the song structure and note shape of
whistles, which in Western Amazonia are always followed by one or more short
notes, a chattering song or downstroke song but in the Atlantic-Cerrado
population, to the extent fragments of downstroke songs can be considered the
equivalent of a whistle, are delivered alone or in sequences of such notes and
have a less symmetrical and more sharply peaked note shape (Figs. 1-2); (iii)
to the extent fragments of downstroke songs can be considered the equivalent of
a whistle, diagnosably and significantly in the maximum acoustic frequency of
whistles (App. 3; Fig. 4A); and (iv) significantly but not diagnosably in other
vocal variables set out in Appendix 3.
· North Amazonian and Atlantic-Cerrado populations differ: (i) in the kind
of primary vocalization, which North Amazonia are whistles and in the
Atlantic-Cerrado are chattering songs (App. 4); and (ii) in the kind of
secondary vocalization, which in North Amazonia are chattering songs and in the
Atlantic-Cerrado are downstroke songs (App. 4); (iii) diagnosably and
significantly in the length of whistles (App. 3; Fig. 4A); (iv) provisionally
(based on a single recording from North Amazonia), in the note shape of
downstroke songs, with the North Amazonia recording having an initial upstroke
which is slower in reaching the peak; and (v) significantly but not diagnosably
in other variables set out in Appendix 3.
· Western Amazonian and North Amazonian populations differ: (i)
diagnosably in the song structure of whistles, which are the primary
vocalization for both populations, which in Western Amazonia are always
followed by one or more short notes, a chattering song or downstroke song but
in North Amazonia are delivered alone or in sequences of whistles; (ii)
significantly in maximum acoustic frequency of whistles (App. 3; Fig. 4A),
which narrowly missed the statistical test of diagnosability perhaps due to
sample sizes from North Amazonia, but showed no overlap; (iii) in secondary
vocalization type (which is the chattering song in North Amazonia versus downstroke
song in West Amazonia) (App. 4); (iv) provisionally (based on a single
recording from North Amazonia), in the note shape of downstroke songs, with the
North Amazonia recording having an initial upstroke which is slower in reaching
the peak; and (v) significantly but not diagnosably in other variables set out
in Appendix 3.
Distributions and country lists
Most textbooks show a widespread range for Sirystes, but as noted in Donegan (2013) there is almost no
evidence for the species occurring in southern Amazonia or much of western
Amazonia, whilst all other parts of the genus' distribution are corroborated by
multiple specimen, sound recording and trip report based/reserve list
records. (See map below). Populations
appear restricted to particular habitats/biogeographical regions (the Choco,
western Amazonia (both sides of the Amazon river), North Amazonia and Atlantic
& Cerrado) rather than to interfluves.
The only population limited by a river is Todd's Sirystes in the
southern part of its range, which is limited by the lower Amazon River (in its
widest part).
Vernacular names
The vernacular names would be those set out in
the Abstract quoted above, which are those of Hellmayr (1927) except that for
"Western Sirystes", which is Ridgely & Greenfield (2001)'s
preference over Ridgway (1907) and Hellmayr (1927)'s "Panama
Sirystes". If
Part B passes, then the "Western/Eastern" nomenclature becomes less
attractive and "Choco Sirystes" could be used instead of
"Western" for albogriseus. Given what happened to the Schiffornis, compass direction-based
names seem better avoided. I will do a
separate proposal on the three 'available' English names for albogriseus in the event that Part B
passes.
References
Donegan,
T.M. 2013b. Vocal variation and species limits in the genus Sirystes (Tyrannidae). Conservación Colombiana 19: 11-30.
The paper can be accessed from this
link:
http://www.proaves.org/birds-of-colombia-2013/?lang=en
Other references are cited in the above.
Thomas Donegan,
December 2013
Comments
from Remsen: “YES to
both A and B. Donegan’s published
analyses shows that multiple species should be recognized.”
Comments from Stiles: “A definite YES to
part A: this split is well documented and widely accepted. For part B, given
their vocal distinctiveness and relatively less extreme plumage differences as
well as the convincing analogy with the closely related Myiarchus, I think that the burden of proof has shifted towards
those who would treat all three as a single species, so YES.”
Comments from Pacheco: “Yes (A) due to of reasons given by Donegan's paper, in
accordance with the existing literature data. A Yes (B) also based on that
article and my own experience.”
Comments from Nores: “A: YES. B: NO.
I repeat here what I put in proposal 49: “Separar especies por suaves diferencias en el canto
no me parece bien. Recientemente estuve en el noreste de Brasil y me llamó la
atención lo diferente que son los cantos de algunas subespecies de allí con
respecto a las poblaciones del sur de Sudamérica. Por ejemplo, Thraupis sayaca tiene un canto mucho mas
potente y mas variado que las razas del sur y Turdus rufiventris emite un llamado permanente que nunca se lo
escuché a la subespecie de esta latitud. Otro notable ejemplo es Vanellus chilensis, del cual la raza del
sur de Argentina y Chile emiten un canto bastante diferente (parece un loro)
que la raza que habita el norte y centro de Argentina hasta Amazonas. Esto no
significa para mi que haya que elevar las subespecies a especies."
Comments
from Zimmer: “YES to
both A and B. The vocal distinctions
between the various populations of Sirystes have long been obvious to those
with the required geographic breadth of field experience, and Donegan has done
a good job of detailing that in his paper.
He has also done a good job of highlighting the apparent patchy
distribution of Sirystes as a whole, something that squares with my experience,
but which flies counter to most published range descriptions. These are suboscine birds (unlike the
examples of Thraupis and Turdus mentioned by Manuel), and I see
no reason not to treat their diagnosably different vocalizations as hard-wired,
genetically based characters that are at least on a par with any plumage
characters as being reflective of species-level relationships (or lack
thereof).”
Comments from Robbins: “YES, to
recognizing four Sirystes
species. I did not appreciate that the
distribution of the cis-Andean taxa was far more restricted than what the
literature has indicated.
Differentiation in plumage and vocalizations are indeed analogous to Myiarchus species.”